The present invention generally relates to the manufacture of molded parts and in particular a thermal cooled mold form.
Conventionally, mold forms are manufactured from such materials as aluminum, steel or wood. In the case of steel and aluminum, expensive casting or cutting machinery is required for producing the final formed shape. After the design is formed, the mold requires hand finishing to finalize certain complex features of the mold. Further, cooling passages must then be installed into the steel or aluminum to provide means for maintaining the mold within a certain temperature range during its use. As a result, a large or complicated mold may require many weeks to complete. Although steel or aluminum molds provide a high quality mold form, the life use of these types of molds may exceed the life of the final product production. Therefore, in many cases a steel or aluminum mold is very expensive relative to the benefits of the final molded piece.
Wood molds are undeniably cheaper than the aforementioned steel or aluminum molds, but still requires a labor intensive manufacturing procedure to produce a quality mold. A wood mold involves no cooling system, thereby causing excessive press time in the manufacturing process. Wood tools, without a cooling system, causes unpredictable shrinkage in the manufactured part. The durability of wood tools is very short.
It is therefore desirable to provide a mold and a method for constructing the mold which can be manufactured quickly, and at less cost to the manufacturer without measurably affecting durability.
The present invention addresses the aforementioned concerns by providing a mold having a mold surface made of a polymer resin, in particular polyurea or a polyurea blend, polyurethanes or a polyurethane blend. The procedure to manufacture the mold piece includes forming a wax or wood pattern having a surface of the shape of the final molded piece, and then building a box structure around the wax or wood pattern. The wax or wood pattern is then sprayed with a polyurea or polyurethane material to completely coat the surface of the wax or wood structure. Cooling lines are placed within the box structure. After the polyurea or polyurethane material has dried/cured, aluminum puffs/pellets and an epoxy material mix is then inserted into the cavities of the mold. Mold support structures and stanchions may be placed within the box to provide strength and stability to the polyurea or polyurethanes mold as well as to provide additional heat transfer material to the mold. Another layer of polyureas or polyurethanes may be sprayed within the mold. After drying/curing, a vacuum plate is placed over the box structure providing exterior connections to the cooling lines as well as connections to the vacuum hole. The original wax or wood structure is then removed leaving a smooth mold surface made out of the polyurea or polyurethane material and/or blends.
The resulting mold and its process provides a quick, inexpensive and durable mold. Cooling lines are easily installed and eliminate the need of machining into steel or aluminum. Vacuum holes are able to be drilled throughout the mold at a much faster rate than into steel or aluminum. The support structures provide a heat transfer element during the molding process in addition to providing support to the mold structure.
Other objects, advantages and applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings.